Hydrocarbon reforming catalyst, method of preparing the hydrocarbon reforming catalyst, and fuel cell employing the hydrocarbon reforming catalyst

ABSTRACT

A hydrocarbon reforming catalyst, a method of preparing the hydrocarbon reforming catalyst, and a fuel cell including the hydrocarbon reforming catalyst. The hydrocarbon reforming catalyst includes a nickel active catalyst layer loaded on an oxide carrier, and a metal oxide.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2008-0131200, filed on Dec. 22, 2008, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein, byreference.

BACKGROUND

1. Field

The present teachings relate to a hydrocarbon reforming catalyst, amethod of preparing the hydrocarbon reforming catalyst, and a fuel cellemploying the hydrocarbon reforming catalyst.

2. Description of the Related Art

Recently, new environmentally friendly energy technologies have comeinto the spotlight. In particular, fuel cells are gaining attention asone such environmentally friendly energy technology. A fuel cellconverts chemical energy into electric energy, by electrochemicallyreacting hydrogen and oxygen. A fuel cell has a high energy efficiency,and studies regarding the practical use of fuel cells in consumer,industrial, and vehicular applications are actively being performed.

Methanol, liquefied natural gas mainly including methane, city gashaving the liquefied natural gas as the main component, synthesizedliquid fuel having natural gas as a raw material, and petroleum-basedhydrocarbons, such as naphtha or kerosene, are being studied as hydrogensources for fuel cells.

When hydrogen is prepared by using a petroleum-based hydrocarbon, asteam reforming reaction using a catalyst is performed on thepetroleum-based hydrocarbon. Here, a conventional carrier containing aruthenium active component has been studied for use as the catalyst forthe steam reforming reaction. Also, catalysts based on cerium oxide, orzirconium oxide, and ruthenium are being studied, since a promotereffect has been discovered for such catalysts. Besides ruthenium,studies regarding catalysts including platinum, rhodium, palladium,iridium, or nickel, as an active component, are also performed.

SUMMARY

The present teachings relate to a hydrocarbon reforming catalyst.

The present teachings relate to a method of preparing the hydrocarbonreforming catalyst.

The present teachings relate to a fuel cell employing the hydrocarbonreforming catalyst.

One or more embodiments of the present teachings relate to a hydrocarbonreforming catalyst including: a nickel active catalyst layer and a metaloxide, supported on an oxide carrier. The metal oxide may be at leastone of a manganese oxide, a tin oxide, a cerium oxide, a rhenium oxide,a molybdenum oxide, and a tungsten oxide. The oxide carrier may beformed of at least one oxide of Al₂O₃, SiO₂, ZrO₂, TiO₂, andyttria-stabilized zirconia (YSZ).

According to various embodiments, the metal oxide may be distributed onand/or in the nickel active catalyst layer.

According to various embodiments, the amount of nickel may be from about1.0 to 40 parts by weight, based on 100 parts by weight of thehydrocarbon reforming catalyst.

According to various embodiments, the amount of metal in the metal oxidemay be from about 0.5 to 20 parts by weight, based on 1 part by weightof nickel.

Various embodiments of the present teachings relate to a method ofpreparing a hydrocarbon reforming catalyst, the method including:loading nickel on an oxide carrier; heat-treating the nickel-loadedoxide carrier; loading a metal oxide precursor on the heat-treatednickel-loaded oxide carrier; and heat-treating the resultant.

To achieve the above and/or other aspects, one or more embodiments mayinclude a method of preparing a hydrocarbon reforming catalyst, themethod including: loading a metal oxide precursor on an oxide carrier;heat-treating the precursor-loaded oxide carrier; loading nickel on theheat-treated precursor-loaded oxide carrier; and heat-treating theresultant.

Various embodiments of the present teachings relate to a method ofpreparing a hydrocarbon reforming catalyst, the method includingsimultaneously loading a metal oxide precursor and nickel on an oxidecarrier, and heat-treating the resultant.

According to various embodiments, the loading of the nickel and theloading of the metal oxide precursor may be performed using depositionprecipitation, co-precipitation, wet impregnation, sputtering, gas-phasegrafting, liquid-phase grafting, or incipient-wetness impregnation.

According to various embodiments, the heat-treating may be performed forfrom about 2 to 5 hours, at from about 500 to 750° C.

To achieve the above and/or other aspects, one or more exemplaryembodiments may include a fuel cell including the hydrocarbon reformingcatalyst.

Additional aspects and/or advantages of the present teachings will beset forth in part in the description which follows and, in part, will beobvious from the description, or may be learned by practice of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the present teachings willbecome apparent and more readily appreciated from the followingdescription of the exemplary embodiments, taken in conjunction with theaccompanying drawings, of which:

FIG. 1 is a diagram schematically illustrating a structure of ahydrocarbon reforming catalyst, according to an exemplary embodiment;

FIGS. 2 through 4 are diagrams for describing methods of preparing ahydrocarbon reforming catalyst, according to exemplary embodiments; and

FIGS. 5 through 8 are graphs showing results of evaluating theperformance of hydrocarbon reforming catalysts obtained according toExamples 1 and 2, and Comparative Example 1.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Reference will now be made in detail to the exemplary embodiments of thepresent teachings, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The exemplary embodiments are described below, in order toexplain the aspects of the present teachings, by referring to thefigures.

Herein, when a first element is referred to as being “loaded on” or“supported by” a second element, the first element can be dispersed onthe surface of the element and/or may be dispersed in the secondelement. Herein, when a first element is referred to as being formed ordisposed “on” a second element, the first element can be disposeddirectly on the second element, or one or more other elements may bedisposed therebetween. When a first element is referred to as beingformed or disposed “directly on” a second element, no other elements aredisposed therebetween.

In order to generate hydrogen fuel for a fuel cell system, a hydrocarbonreforming catalyst accelerates a steam reforming (SR) reaction, whereinthe hydrocarbon is reacted with steam at a high temperature, accordingto Reaction Formula 1, below.

C_(n)H_(m) +nH₂O→nCO+(n+m/2)H₂   Reaction Formula 1

The amount of CO gas in the reformate generated according to ReactionFormula 1 is minimized, via a water gas shift reaction, wherein the COgas reacts with steam at a temperature of from about 200 to 400° C. andis converted into carbon dioxide and hydrogen, as shown in ReactionFormula 2, below.

CO+H₂O→CO₂+H₂   Reaction Formula 2

Such a reforming reaction progresses catalytically at temperatures offrom about 600 to 900° C. Therefore, a relatively high reformingreaction rate (i.e. a catalytic activity), coking resistance (i.e.carbon deposition suppression), and high temperature thermal stability(i.e. durability), are generally sought after in a reforming catalystfor the reforming reaction.

In a hydrocarbon reforming catalyst, according to an exemplaryembodiment of the present teachings, nickel as an active catalyst and ametal oxide as a co-catalyst are supported on an oxide carrier. Thehydrocarbon reforming catalyst exhibits excellent catalytic activity.Also, a high coking resistance and long-term thermal stability of thehydrocarbon reforming catalyst are obtained, by using the metal oxide.

The oxide carrier may be a conventional oxide carrier used in areforming catalyst. The oxide carrier may have a porous structure havinga high surface area. The oxide carrier may be formed of at least oneoxide selected from among Al₂O₃, SiO₂, ZrO₂, TiO₂, and yttria-stabilizedzirconia (YSZ).

The hydrocarbon reforming catalyst includes a nickel layer as an activecomponent. Nickel has an excellent catalytic activity and a low price,as compared to ruthenium, platinum, rhodium, palladium, and iridium,which are used as conventional active components of a reformingcatalyst. The amount of nickel may be from about 1.0 to 40 parts byweight, based on 100 parts by weight of the hydrocarbon reformingcatalyst. The nickel can be formed as a continuous or discontinuouslayer on the oxide carrier.

The hydrocarbon reforming catalyst may include at least one metal oxideco-catalyst selected from among a manganese oxide, a tin oxide, a ceriumoxide, a rhenium oxide, a molybdenum oxide, and a tungsten oxide. When asaturated hydrocarbon, or an unsaturated hydrocarbon having a highcarbon number, is used in a fuel cell system, carbon may besignificantly deposited during a reforming reaction, thereby causing areduction in the performance of the hydrocarbon reforming catalyst. Whencarbon is excessively accumulated in a reactor, the pressure in thereactor increases, and thus, it is difficult to continue the reformingreaction. The present hydrocarbon reforming catalysts include the metaloxide, thereby preventing the deposition of carbon. The amount of themetal in the metal oxide may be from about 0.5 to 20 parts by weight,based on 1 part by weight of nickel.

The metal oxide may be distributed on the surface of and/or within anickel active catalyst layer. FIG. 1 is a diagram schematicallyillustrating the structure of a hydrocarbon reforming catalyst 10,according to an exemplary embodiment of the present teachings.

Referring to FIG. 1, the hydrocarbon reforming catalyst 10 includes anoxide carrier 11, a nickel active catalyst layer 12, and a metal oxide13. The nickel active catalyst layer 12 is supported on the oxidecarrier 11, and the metal oxide 13 is distributed on the nickel activecatalyst layer 12. Although not limited in theory, a coking site 14,where carbon is deposited during a reforming reaction, may be formed onthe surface of the nickel active catalyst layer 12. The activity of thehydrocarbon reforming catalyst 10 may be improved, if the metal oxide 13blocks the coking site 14.

A hydrocarbon reforming catalyst, according to another exemplaryembodiment of the present teachings, has a nickel active catalyst andmetal oxide co-catalyst that are structurally mixed and supported on anoxide carrier. The metal oxide may exist on the surface of and/or withina layer of the nickel, according to some exemplary embodiments. Althoughnot limited in theory, the mixture of the metal oxide and the nickel maysuppress the formation of a coking site in the nickel active catalyst.

A method of preparing a hydrocarbon reforming catalyst, according toexemplary embodiments of the present teachings, will now be described.As illustrated in FIGS. 2 through 4, a hydrocarbon reforming catalystmay be prepared, by simultaneously loading a nickel precursor and ametal oxide precursor on an oxide carrier. Alternatively, the nickelprecursor and the metal oxide precursor may be sequentially loaded, inthat order.

Referring to FIG. 2, the method includes: loading the nickel precursoron an oxide carrier; heat-treating the nickel precursor-loaded oxidecarrier, to form a nickel active catalyst layer; loading a metal oxideprecursor on the nickel active catalyst layer; and heat-treating theresultant.

Any one of various well known methods may be used to load the nickelprecursor and the metal oxide precursor on the oxide carrier. Forexample, methods such as deposition precipitation, co-precipitation, wetimpregnation, sputtering, gas-phase grafting, liquid-phase grafting, andincipient-wetness impregnation may be used. When a loading method thatdoes not use a liquid medium is used, a drying process as describedbelow may be omitted.

For example, when the nickel precursor is loaded via wet impregnation, amixed solution is prepared by adding and uniformly mixing a nickelprecursor solution and an oxide carrier. As described above, the oxidecarrier may be selected from among Al₂O₃, SiO₂, ZrO₂, TiO₂, and YSZ. Thenickel precursor solution may be prepared by dissolving a nickel salt ina solvent, such as water; an alcohol-based solvent such as methanol,ethanol, isopropyl alcohol, or butyl alcohol; or a mixture thereof. Theconditions for mixing the nickel precursor solution and the oxidecarrier are not specifically limited. For example, the nickel precursorsolution and the oxide carrier may be stirred for from about 1 to 12hours, at from about 40 to 80° C. The nickel salt may be a nickelhalide, including chloride or fluoride, a nickel nitrate, a nickelsulfate, a nickel acetate, or a mixture thereof.

The mixed solution is dried, for example, for from about 3 to 5 hours,at 100 to 160° C. The dried mixed solution is then heat-treated toobtain a heat-treated product. For example, the heat-treated product,where nickel is loaded on the oxide carrier, may be obtained byheat-treating the dried mixed solution for from about 2 to 5 hours, atfrom about 500 to 750° C. The heat-treatment may be performed in anoxidation atmosphere, for example, in an air atmosphere.

Next, the metal oxide precursor is loaded on the heat-treated product,according to the same method used for loading the nickel precursor. Forexample, when wet impregnation is used, a metal oxide precursor solutionmay be prepared by dissolving: a metallic salt in the above describedsolvent. The metal oxide precursor solution is uniformly mixed with anoxide carrier. The metal salt may include a halide, such as a chlorideor fluoride, a nitrate, a sulfate, or an acetate, of at least one metalselected from among manganese, tin, cerium, molybdenum, and tungsten.

Then, by performing the drying and heat-treating processes as describedabove, the metal oxide precursor is oxidized into a metal oxide.Accordingly, the hydrocarbon reforming catalyst 10 of FIG. 1 is formed.

Referring to FIG. 3, the method according to another exemplaryembodiment includes: loading a metal oxide precursor on an oxidecarrier; heat-treating the precursor-loaded oxide carrier, to form ametal oxide-loaded carrier; loading nickel on the metal oxide-loadedcarrier; and heat-treating the resultant. The method of FIG. 3 isperformed in the same manner as the method of FIG. 2, except that themetal oxide and the nickel are sequentially loaded on the oxide carrier,in that order. Accordingly, a hydrocarbon reforming catalyst including anickel/metal oxide/oxide carrier may be obtained.

Referring to FIG. 4, the method includes simultaneously loading a nickelprecursor and a metal oxide precursor on an oxide carrier, andheat-treating the resultant. When the nickel and the metal oxideprecursors are simultaneously loaded, via, for example, wetimpregnation, an oxide carrier is uniformly mixed with a solutionincluding both the nickel precursor and the metal oxide precursor, andthen the resultant is dried. The nickel precursor, the metal oxideprecursor, and the solvent are as described above.

In some aspects, an additional amount of the metal oxide precursor orthe metal oxide may be loaded on the hydrocarbon reforming catalyst. Thehydrocarbon reforming catalyst may be processed for from about 1 to 2hours, at 600 to 950° C., in a hydrogen atmosphere, before being usedfor a reforming reaction.

According to another exemplary embodiment, a fuel processing apparatusincluding the hydrocarbon reforming catalyst is provided. The fuelprocessing apparatus may be obtained by manufacturing a reformingapparatus including the hydrocarbon reforming catalyst, and thenmanufacturing the fuel processing apparatus including the reformingapparatus. The hydrocarbon reforming catalyst may be fixed to a tubularreactor or a mixed flow reactor, but the present teachings are notlimited thereto.

The exemplary embodiments will be described in greater detail withreference to the following examples. The following examples are forillustrative purposes only and are not intended to limit the scope ofthe present teachings.

<Preparation of Catalyst>

Example 1

30.4 g of an Ni(NO₃)₂.H₂O (Aldrich) nickel precursor was impregnatedinto 100 g of an Al₂O₃ carrier (Alfa, particle size: 100 μm, surfacearea: 150 m²g⁻¹), so that the amount of Ni in a final catalyst was 5 wt%. The mixture thereof was dried for 24 hours at 110° C., and then wascalcined for 2 hours, at 700° C., in an air atmosphere.

Then, 46.77 g of an Mn(NO₃)₂.H₂O manganese oxide precursor wasimpregnated into the resultant calcined product, such that a weightratio of Mn/Ni was 1:1. The mixture thereof was dried for 24 hours at110° C. and then calcined for 2 hours at 700° C., so as to obtain anMnO_(x)/Ni/Al₂O₃ hydrocarbon reforming catalyst.

Example 2

An Ni-MnO_(x)/Al₂O₃ hydrocarbon reforming catalyst was obtainedaccording to the same manner as Example 1, except that the nickelprecursor and the manganese oxide precursor were simultaneouslyimpregnated into the Al₂O₃ carrier.

Comparative Example 1

An Ni/Al₂O₃ hydrocarbon reforming catalyst was obtained in the samemanner as Example 1, except that the impregnation of the manganeseprecursor and the associated operations were omitted.

<Performance Evaluation of Catalyst>

Evaluation Example 1

Propane conversions over the hydrocarbon reforming catalysts prepared inExamples 1 and 2, and Comparative Example 1 were measured over time,under the following operation conditions, and the results are shown inFIG. 5.

Reaction Temperature: 873 K,

Gas Hourly Space Velocity (GHSV)=32,000 h⁻¹

Gas Composition: Propane 95% and n-Butane 5%

Steam/Carbon Molar Ratio (steam/C)=3

Evaluation Example 2

n-Butane conversions over the hydrocarbon reforming catalysts preparedin Examples 1 and 2, and Comparative Example 1 were measured over time,under the same operation conditions as Evaluation Example 1, except thatn-butane was used instead of propane, and the results are shown in FIG.6.

Evaluation Example 3

Propane conversions over the hydrocarbon reforming catalysts prepared inExamples 1 and 2, and Comparative Example 1 were measured over time,under the following operation conditions, and the results are shown inFIG. 7. Here, the hydrocarbon catalyst of Comparative Example 1exhibited a propane conversion rate of below 80%, after initiallystarting a reforming reaction, but it was impossible to perform thereforming reaction after 1 to 2 hours, due to increased pressure in areactor caused by severe carbon deposition.

Reaction Temperature: 973 K

GHSV=609,000 h⁻¹

Gas Composition: Propane 95% and n-Butane 5%

Steam/Carbon Molar Ratio (steam/C)=3

Evaluation Example 4

n-Butane conversions over the hydrocarbon reforming catalysts preparedin Examples 1 and 2, and Comparative Example 1 were measured over time,under the same operation conditions as Evaluation Example 3, except thatn-butane was used instead of propane, and the results are shown in FIG.8. Here, the hydrocarbon catalyst of Comparative Example 1 exhibited ann-butane conversion rate of below 85% for 1 hour, but was impossible tooperate after 2 hours, due to severe carbon deposition.

Evaluation Example 5

The hydrocarbon reforming catalysts of Examples 1 and 2, and ComparativeExample 1 were operated for 10 hours, under the same operatingconditions as Evaluation Example 3, the hydrocarbon reforming catalystswere collected from a reactor, and then carbon deposition ratios of thehydrocarbon reforming catalysts were measured using a thermogravimetricanalysis (TGA). The carbon deposition ratios were calculated as follows.

Carbon Deposition Ratio=(Weight of Heat Loss)/(Weight of Sample)×100

The results of measuring the carbon deposition rates are shown in Table1 below.

TABLE 1 TGA (Carbon Deposition Rate, %) Example 1 11 Example 2 11Comparative 64 Example 1

Referring to FIGS. 5 through 8, the hydrocarbon reforming catalysts ofExamples 1 and 2 had excellent reactivity, even during a long operation.Also, referring to Table 1, the carbon deposition rates of thehydrocarbon reforming catalysts of Examples 1 and 2 were low.

As described above, according to the one or more of the above exemplaryembodiments, a hydrocarbon reforming catalyst having excellent cokingresistance is provided.

It should be understood that the exemplary embodiments described hereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each exemplaryembodiment should typically be considered as available for other similarfeatures or aspects in other exemplary embodiments.

Although a few exemplary embodiments of the present invention have beenshown and described, it would be appreciated by those skilled in the artthat changes may be made in these exemplary embodiments, withoutdeparting from the principles and spirit of the present teachings, thescope of which is defined in the claims and their equivalents.

1. A hydrocarbon reforming catalyst comprising: an oxide carrier; anickel active catalyst layer disposed on the oxide carrier; and a metaloxide.
 2. The hydrocarbon reforming catalyst of claim 1, wherein themetal oxide is at least one co-catalyst selected from a group consistingof a manganese oxide, a tin oxide, a cerium oxide, a rhenium oxide, amolybdenum oxide, and a tungsten oxide.
 3. The hydrocarbon reformingcatalyst of claim 1, wherein the oxide carrier is formed of at least oneoxide selected from the group consisting of Al₂O₃, SiO₂, ZrO₂, TiO₂ andyttria-stabilized zirconia(YSZ).
 4. The hydrocarbon reforming catalystof claim 1, wherein the metal oxide is distributed on the surface of thenickel active catalyst layer.
 5. The hydrocarbon reforming catalyst ofclaim 1, wherein the metal oxide is distributed within the nickel activecatalyst layer.
 6. The hydrocarbon reforming catalyst of claim 1,wherein the metal oxide is distributed on the surface of and within thenickel active catalyst layer.
 7. The hydrocarbon reforming catalyst ofclaim 1, wherein the amount of the nickel is from about 1.0 to about 40parts by weight based on 100 parts by weight of the hydrocarbonreforming catalyst.
 8. The hydrocarbon reforming catalyst of claim 1,wherein an amount of metal of the metal oxide is from about 0.5 to about20 parts by weight based on 1 part by weight of the nickel.
 9. A methodof preparing a hydrocarbon reforming catalyst, the method comprising:loading a nickel precursor onto an oxide carrier to form a nickelprecursor-loaded carrier; heat-treating the nickel precursor-loadedcarrier to form a nickel active catalyst layer; loading a metal oxideprecursor on the nickel active catalyst layer and heat-treating theresultant to form a metal oxide.
 10. The method of claim 9, wherein theloading of the nickel precursor and the loading of the metal oxideprecursor are performed by deposition precipitation, co-precipitation,wet impregnation, sputtering, gas-phase grafting, liquid-phase grafting,or incipient-wetness impregnation.
 11. The method of claim 9, whereinthe heat-treating is performed for from about 2 to about 5 hours at fromabout 500 to 750 about C°.
 12. The method of claim 9, wherein the metaloxide is at least one co-catalyst selected from the group consisting ofa manganese oxide, a tin oxide, a cerium oxide, a rhenium oxide, amolybdenum oxide, and a tungsten oxide.
 13. The method of claim 9,wherein the oxide carrier is formed of at least one oxide selected fromthe group consisting of Al₂O₃, SiO₂, ZrO₂, TiO₂ and yttria-stabilizedzirconia(YSZ).
 14. A method of preparing a hydrocarbon reformingcatalyst, the method comprising: loading a metal oxide precursor on anoxide carrier to form a metal oxide precursor-loaded oxide carrier;heat-treating the metal oxide precursor-loaded oxide carrier to form ametal oxide-loaded oxide carrier; loading a nickel precursor on themetal oxide-loaded oxide carrier to form a resultant; and heat-treatingthe resultant to form a nickel active catalyst layer.
 15. A method ofpreparing a hydrocarbon reforming catalyst, the method comprising:simultaneously loading a metal oxide precursor and a nickel precursor onan oxide carrier to form a resultant; and heat-treating the resultant toform the hydrocarbon reforming catalyst.
 16. A fuel cell comprising thehydrocarbon reforming catalyst according to claim
 1. 17. A fuel cellcomprising the hydrocarbon reforming catalyst according to claim
 2. 18.A fuel cell comprising the hydrocarbon reforming catalyst according toclaim
 3. 19. A fuel cell comprising the hydrocarbon reforming catalystaccording to claim
 4. 20. A fuel cell comprising the hydrocarbonreforming catalyst according to claim 5.